Nick Piggin 945754a175 mm: fix race in COW logic ... There is a race in the COW logic. It contains a shortcut to avoid the COW and reuse the page if we have the sole reference on the page, however it is possible to have two racing do_wp_page()ers with one causing the other to mistakenly believe it is safe to take the shortcut when it is not. This could lead to data corruption. Process 1 and process2 each have a wp pte of the same anon page (ie. one forked the other). The page's mapcount is 2. Then they both attempt to write to it around the same time... proc1 proc2 thr1 proc2 thr2 CPU0 CPU1 CPU3 do_wp_page() do_wp_page() trylock_page() can_share_swap_page() load page mapcount (==2) reuse = 0 pte unlock copy page to new_page pte lock page_remove_rmap(page); trylock_page() can_share_swap_page() load page mapcount (==1) reuse = 1 ptep_set_access_flags (allow W) write private key into page read from page ptep_clear_flush() set_pte_at(pte of new_page) Fix this by moving the page_remove_rmap of the old page after the pte clear and flush. Potentially the entire branch could be moved down here, but in order to stay consistent, I won't (should probably move all the *_mm_counter stuff with one patch). Signed-off-by: Nick Piggin <npiggin@suse.de> Acked-by: Hugh Dickins <hugh@veritas.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2008-06-23 11:28:32 -07:00
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allocpercpu.c
backing-dev.c
bootmem.c
bounce.c
dmapool.c
fadvise.c
filemap_xip.c
filemap.c
fremap.c
highmem.c
hugetlb.c
internal.h
Kconfig
maccess.c
madvise.c
Makefile
memcontrol.c
memory_hotplug.c
memory.c	mm: fix race in COW logic	2008-06-23 11:28:32 -07:00
mempolicy.c
mempool.c
migrate.c
mincore.c
mlock.c
mmap.c
mmzone.c
mprotect.c
mremap.c
msync.c
nommu.c
oom_kill.c
page_alloc.c
page_io.c
page_isolation.c
page-writeback.c
pagewalk.c
pdflush.c
prio_tree.c
quicklist.c
readahead.c
rmap.c
shmem_acl.c
shmem.c
slab.c	Slab: Fix memory leak in fallback_alloc()	2008-06-21 16:51:02 -07:00
slob.c
slub.c
sparse-vmemmap.c
sparse.c
swap_state.c
swap.c
swapfile.c
thrash.c
tiny-shmem.c
truncate.c
util.c
vmalloc.c
vmscan.c
vmstat.c